M&S says

Hidden within your shoe, these cotton rich footsies are the solution to chafing problems with shoes, and are specifically designed for extra comfort. These hidden footsies also feature Freshfeet™ technology which fights bad-smelling odours, keeping you comfortable and fresh no matter what you’re doing.

Style

Care and Composition

35 days to return
You may return unused products within 35 days of purchase with a valid parcel summary document. Your items don't need to be in the original box or bag as long as they're securely packaged.

How to return
Simply use our returns portal to print a returns label and returns note. You will then be able to return all or part of your order at your own cost through your preferred carrier. To create a returns label, visit our returns portal select this option and follow the instructions.